Check that private subnets are excluded in the "Integrated" mode

[ameshkov]

This task requires cooperating with the server-side.

There are two options of excluding the local network in the IPSec case.

• First, we could set excludeLocalNetworks to true when configuring the connection. In this case, the tunnel should ignore the routes that it receives from the server-side.
• Second, they could be configured on the server-side.

In theory, we're currently using the second option. However, we received a couple of complaints that private subnets aren't excluded when using the Integrated mode.

Here's what we should do:

1. Check if it's excluded or not (try opening some intranet website when AdGuard VPN is enabled).
2. If it's not, try setting excludeLocalNetworks and see if we can control routes on the client side.
3. If we can control it on the client-side, we should do it this way as it allows us have client-specific routes.

Again, ideally, I'd prefer to have a low-level setting that controls excluded routes (like I explained here: https://github.com/AdguardTeam/AdGuardVPNForiOS/issues/151).